Role of plasminogen, plasmin, and plasminogen activators in the migration of fibroblasts into plasma clots

Human diploid fibroblasts were seeded onto or into plasma clots and different aspects of cell adhesion and migration were measured. The roles of plasminogen activators and plasmin were studied by either the removal of plasminogen from plasma prior to clotting or by the addition of 10 mM epsilon-aminocaproic acid, which brings about an inhibition of plasmin in this system. When cells were seeded onto the surface of plasma clots, rates of attachment, spreading, and migration were unaffected by plasminogen depletion or plasmin inhibition. In contrast, when cells were seeded into plasma clots, then, although the rates of cells spreading were unaffected, cell migration was abolished by plasminogen depletion or by plasmin inhibition. When cells were seeded onto the surface of plasma clots and the rate of migration into the clots was measured, there was an absolute requirement for plasmin activity; while fibroblasts migrated rapidly into the fibrin lattice of control clots, in the case of plasminogen-depleted clots, cells failed to penetrate the lattice. Focussing through a plasma clot revealed that fibroblasts do not migrate through the fibrin lattice but instead, localized areas of fibrinolysis are generated and cells migrate over the surface of the area of lysis.     

Inhibition of DNA synthesis in proliferating human diploid fibroblasts by fusion with senescent cytoplasts

Cytoplasts were prepared from senescent human diploid fibroblasts. The cytoplasts were fused to young human diploid fibroblasts and DNA synthesis was analyzed in the fusion products. DNA synthesis was inhibited (greater than or equal to 40%) in the senescent cytoplast fusion products when compared to unfused young cells or young cytoplasts fused with young cells. These results are consistent with previous experiments that have shown the blockage of DNA synthesis in both nuclei of heterokaryons from fusions of senescent and young human diploid fibroblast cells. Furthermore, these results support the postulate that senescent cells synthesize a specific substance(s), which is present in the cytoplasm of the senescent cell that inhibits DNA synthesis.     

Changes of serum-induced ornithine decarboxylase activity and putrescine content during aging of IMR-90 human diploid fibroblasts

The roles of ornithine decarboxylase (ODC, EC 4.1.1.17) and polyamines in cellular aging were investigated by examining serum-induced changes of these parameters in quiescent IMR-90 human diploid fibroblasts as a function of their population doubling level (PDL) and in human progeria fibroblasts. Serum stimulation caused increases of ODC and DNA synthesis in IMR-90 human diploid fibroblasts, with maximal values occurring, respectively, 10 hr and 22 hr after serum stimulation. Both serum-induced ODC activity and DNA synthesis in IMR-90 cells were found to be inversely related to their PDL. Maximal ODC activity and DNA synthesis in young cells (PDL = approximately 18-22) were, respectively, five-fold and six-fold greater than that in old cells (PDL = approximately 50-55), which in turn were comparable or slightly higher than that in progeria fibroblasts. Polyamine contents (putrescine, spermidine, and spermine) in quiescent IMR-90 cells did not show significant PDL-dependency. The putrescine and spermine contents in quiescent progeria cells were comparable to those in quiescent IMR-90 cells. The spermidine content in quiescent progeria cells, however, was extremely low, less than half of that in quiescent IMR-90 cells. Serum stimulation caused a marked increase in putrescine content in young cells but not in old cells or in progeria cells. The spermidine and the spermine content in IMR-90 cells, either young or old, and in progeria cells did not change significantly after serum stimulation. Our study indicated that aging of IMR-90 human diploid fibroblasts was accompanied by specific changes of polyamine metabolism, namely, the serum-induced ODC activity and putrescine accumulation. These changes were also observed in progeria fibroblasts derived from patients with Hutchinson-Gilford syndrome.     

Down's syndrome,Edwards' syndrome,Patau's syndrome —synthesis of glycosaminoglycans

Synthesis of glycosaminoglycans (GAGS) by fibroblasts derived from seven patients with Down's syndrome, five patients with Edwards' syndrome, and two patients with Patau's syndrome were studied in cell culture. The aneuploid strains were compared with diploid fibroblasts from age-matched controls. In terms of hyaluronic acid and sulfated GAG synthesis, the amount of synthesized hyaluronic acid was not significantly different between postnatal aneuploid strains and controls.     

Migration and proliferation of diploid human fibroblasts following "wounding" of confluent monolayers

Six diploid human fibroblast strains were grown in confluent monolayers. Holes were scraped in these monolayers and the number of cells proliferating into these “wounds” with time were determined. The migration and mitotic aspects of the proliferation of fibroblasts into these wounds were analyzed separately. Small amounts of undialysed or dialysed serum were essential for cell division but not migration. Saline extracts of skin could not substitute for serum in the medium. Neither zinc nor cupric ion at tolerable concentrations (10^?5M) increased the rate of cell proliferation. Normal human fibroblasts did not immediately start to divide from confluency into the “wound” space. Their generation time was about 32–39 hours. Fibroblasts from patients with cystic fibrosis began to divide almost immediately into the “wounded” area. Their generation time was about 48 to 56 hours.     

Difference between diploid and aneuploid Chinese hamster cells in replication at mid-S-phase

Following partial synchronization of the heteroploid Chinese hamster cell line V-79 and of normal diploid lung fibroblasts of the Chinese hamster in culture, their DNA replication during S-phase was compared by means of a BrdU-incorporation/thymidine pulse technique and Hoechst-Giemsa differential staining of metaphase chromosomes. This comparison indirectly shows the S-phase of the heteroploid cells of V-79 to be 2 h shorter than the diploid cell S-phase. When the thymidine pulse is applied to diploid lung fibroblasts at mid-S-phase, differential staining colours metaphase chromosomes a pale blue. Performing the corresponding experiment with V-79 cells, neither a pale blue nor dark red staining is obtained, but rather an intermediate shade, showing prominently dark staining regions in parts. The pause in DNA synthesis observed at mid-S-phase of the diploid Chinese hamster lung fibroblasts seems to be omitted at mid-S-phase of the V-79 cells.     

The nature of thymidine kinase in the human-mouse hybrid cell

In order to characterize the thymidine kinase in human-mouse somatic cell hybrids derived from mouse parental cells lacking thymidine kinase, we have examined the electrophoretic migration on starch gel and the heat sensitivity of this enzyme in human, mouse, and hybrid cells. The enzyme of hybrid cells migrates similarly to that of human fetal liver and human diploid fibroblasts and faster than that of either L or A₉ mouse cells. It is less sensitive to heat than that of the mouse cells. Therefore, the human group E chromosome provides human thymidine kinase for the hybrid cell. The electrophoresis of thymidine kinase makes possible the search for variants.Aided by U.S.P.H.S. Grant No. HD 00486.     

Comparison of pulmonary endothelial cell and fibroblast proliferation using time-lapse cinematographic analysis

Time-lapse cinematography was used to study and compare the proliferation and migration activity of pulmonary endothelial cells and fibroblasts, two cell types with very different structural and functional properties. Endothelial cells were found to have a mere rapid growth rate than fibroblasts. Contributing to the shorter population doubling time of the endothelial cells were lower interdivision times and a tendency for these cells to remain in division cycle with successive generations of growth. Striking differences between endothelial cells and fibroblasts were seen in migration behaviour. Endothelial cells had lower migration rates and tended to remain within a restricted growth area, whereas fibroblasts migrated freely throughout the growth area.     

The action of N-methyl-N-nitrosourea on non-established human cell lines in vitro. I. Cell cycle inhibition and aberration induction in diploid and Down's fibroblasts.

The effect of N-methyl-N-nitrosourea (MNU) on the cell cycle, DNA synthesis and chromosomal sensitivity of cultivated diploid fibroblasts and fibroblasts with trisomy 21 was investigated in vitro. With the exception of the inhibition of G2, Down's cells proved to be more sensitive than diploid cells with respect to the decrease of the mitotic and labelling index, the inhibition of the progression of cells through the early and middle S and the frequency of induced chromosomal aberrations. The chromosomal sensitivity was dependent on the position of cells in the cell cycle during treatment with MNU. If treated during late S no differences concerning the S block and aberration frequencies were found between diploid and Down's cells. However, if MNU treatment took place in the middle and early S, Down's cells were more sensitive. The higher aberration frequencies in Down's cells resulted from elevated levels of chromatid breaks, multiple fragmentations and chromatid translocations. Possible reasons for the increased sensitivity of Down's cells are discussed.     

Drastic change of local stiffness distribution correlating to cell migration in living fibroblasts.

Sequential images of the local stiffness distribution of living fibroblasts (NIH3T3) were captured under a culture condition using scanning probe microscopy in a force modulation mode. We found a clear relation between cell migration and local stiffness distribution on the cell: When cells were stationary at one position, the stiffness distribution of their cellular surface was quite stable. On the other hand, once the cells started to move, the stiffness in their nuclear regions drastically decreased. Possible explanations for the correlation between the cell migration and the cell stiffness are proposed.     

Sea urchin primary mesenchyme cells: relation of cell polarity to the epithelial-mesenchymal transformation

In euechinoid sea urchin embryos, a subset of epithelial cells in the wall of the blastula become pulsatile, elongate, lose connections with their neighboring cells, and move into the blastocoel to form the primary mesenchyme cells. The Golgi apparatus and microtubule organizing center (MTOC) are located at the apical end of these epithelial cells. We show that as primary mesenchyme cells begin to move into the blastocoel, the Golgi apparatus and MTOC move to a new position adjacent to the apical side of the nucleus. They do not move to a position between the nucleus and the leading (i.e., basal) end of the cell as they do in cultured fibroblasts undergoing directed migration. In addition, we have inhibited the movement of membranous vesicles to the cell surface by incubating embryos in the ionophore monensin. We have used antibodies to msp130, a primary mesenchyme cell surface-specific glycoprotein, to demonstrate that monensin inhibits the movement of msp130-containing vesicles to the cell surface. Despite the inhibition of membrane shuttling by monensin, primary mesenchyme cells ingress on schedule and display normal cell-shape changes. We draw two conclusions from our data. First, the cellular elongation that characterizes ingression is not due to the local insertion of membrane at the leading (basal) end of the cell. Second, ingression does not depend upon establishment of the same cell polarity required for fibroblasts to carry out directed cell migration.     

Characteristics of intracellular metabolism of procollagen and other proteins in human embryo fibroblasts in trisomy for chromosome 7

A comparative study of the relative rates of intracellular total protein metabolism in diploid and aneuploid (with trisomy for chromosome 7) human embryo fibroblasts in the logarithmic and stationary growth phases was carried out. Using double labeling with [14C]proline (24 hrs) and [3H]proline (3 hrs), it was found that: the rates of intracellular protein metabolism during transition to the stationary phase of growth are increased in diploid cells and decreased in cells with trisomy for chromosome 7; the relative rate of protein metabolism in the logarithmic phase is higher in trisomic cells than in diploid ones. The intracellular degradation of procollagen in trisomic cells is increased approximately by 17% as compared to normal fibroblasts. Treatment of cell lysates with bacterial collagenase revealed the presence of procollagen incomplete degradation products in anomalous fibroblasts. The observed differences in the rates and mode of protein metabolism during transition of diploid and trisomic fibroblasts to the stationary phase of growth suggest that the odd autosome interferes with the normal coordinated activity of genes in chromosomes.     

Viral-induced fusion of human cells. II. Heterokaryocytes between human cells from different donors, and between human cells and those from other species: formation and properties

A simple method is described for effecting the formation of heterokaryocytes between different lines of human diploid fibroblasts, and between human diploid fibroblasts and cultured cells derived from other species. In the case of mixed monolayer cultures of human diploid fibroblasts exposed to UV-inactivated Sendai virus, the proportion of nuclei in heterokaryocytes is between 25 and 35%. The heterokaryocytes engage in de novo protein synthesis. No evidence of hybrid enzymes was found in mixed cultures of human and mouse cells which had been exposed to Sendai virus and which therefore presumably contained mouse-human heterokaryocytes. However, with the available data, it is not possible to distinguish between the absence of synthesis of hybrid enzymes and the synthesis of hybrid enzymes in amounts insufficient to permit their detection.     

Aging in vitro : Growth of cultured cells from the Galapagos tortoise

Skin biopsies from two growing and two fully-grown Galapagos tortoises, a species that lives twice as long as man, were explanted in vitro. Cellular outgrowth was more vigorous from explants of young tortoises but epithelial cells stopped dividing early in the history of all cultures, even at the optimum temperature of 30 °C. Serially subcultured fibroblasts from young tortoises divided more rapidly and achieved longer lifespans than fibroblasts from old tortoises in terms of mean population doublings and to a lesser extent, calendar time. For all cultures the lifespans exceeded those reported for human diploid fibroblasts. The results indicate that a proportionality exists between the potential (remaining) lifespan in vivo and the mitotic capacity of cultured diploid cells in vitro.     

FISH analysis of regional replication of homologous chromosomes in hybrid cells obtained by fusion of embryonic stem cells with somatic cells

The paper deals with the FISH analysis of the regional replication of homologue of chromosomes 1, 3, and 6 in hybrid cells obtained by the fusion of Mus musculus embryonic stem cells (ESCs) and somatic cells—M. caroli splenocytes. The obtained data showed that, in hybrid cells with near-diploid karyotypes, the parental chromosomes were replicated synchronously in 70–75% of tested cells, similar to in diploid ESCs and diploid fibroblasts. In hybrid cells with near-triploid karyotypes, the asynchronous replication of the parental chromosomes increased to 46–57% of tested cells. However, this is true for hybrid cells with three copies of tested chromosomes, whereas, in triploid cells with two copies, the level of the homolog synchronous replication was close to that of diploid cells. In hybrid cells with near-tetraploid karyotypes, the level of asynchronous replication was observed in more than 50% of cells, which is comparable with the level in tetraploid ESCs and tetraploid fibroblasts. Thus, in hybrid cells with no more than two copies of an individual chromosome, the synchronous replication of homologue that initially had different levels of differentiation and parameters of replications was observed. However, the information value of the method of in situ hybridization on interphase nuclei changes significantly with an increase in the number of copies of individual chromosomes and thereby restricts possibilities of this approach for evaluation of synchronous homolog replication in hybrid cells.     

Role of fibronectin in the migration of fibroblasts into plasma clots

The adhesion and migration of human diploid fibroblasts on plasma clots were measured. The role of plasma fibronectin was examined by depleting plasma of fibronectin before clotting. Fibronectin was not essential for cell adhesion and spreading, although rates were slightly slower on depleted clots. Rates of migration on the surface of clots were unaffected by fibronectin depletion. In contrast, fibronectin was an absolute requirement for migration of cells into plasma clots. Cells migrated rapidly into control clots but completely failed to penetrate the surface of fibronectin-depleted clots. The effect of depletion could only be reversed by adding fibronectin to depleted plasma before clotting. Adsorption of fibronectin after clotting failed to reverse the effect of depletion, suggesting that fibronectin had to be cross-linked by transglutaminase during the clotting process.     

The Role of Cell Proliferation in Tubulogenesis of Human Keratinocytes

We studied kinetics and role of keratinocyte proliferation in the process of cysto- and tubulogenesis of human postnatal epidermal keratinocytes in collagen gel. The influence of media conditioned by embryonic and postnatal fibroblasts on morphogenesis has been comparatively analyzed. We studied the influence of proliferation inhibitors and inductors on tubulogenesis. The obtained data indicate partial dissociation of migration, proliferation, and differentiation of keratinocytes during morphogenetic processes in culture. We propose a new model considering proliferation of epithelial cells during cysto- and tubulogenesis.     

Cell surface changes accompanying aging in human diploid fibroblasts : III. Division age and senescence revealed by concanavalin A-mediated red blood cell adsorption

The relationship between cell size, [³H]thymidine incorporation capacity, and cell surface property of human diploid fibroblasts was investigated using the concanavalin A (ConA)-mediated red blood cell (RBC) adsorption assay. Small cells in late passage populations adsorbed RBCs well with the RBC coating method (in which ConA-coated RBCs are adsorbed to fibroblasts) as did large cells of this population, while small cells in early passage populations did not. The RBC adsorption capacity of rapidly dividing cells with this method differed among young, middle-aged and old cell populations. The results suggest that temporal cell size and [³H]thymidine incorporating capacity is not a measure of the division age of human diploid cells at the individual cell level. On the other hand, RBC adsorption with the fibroblast coating method (in which RBCs are adsorbed to ConA-coated fibroblasts) occurred to non-dividing cells of the populations. Thus, the increase in RBC adsorption with this method is considered to be a reflection of the increase in non-dividing cells at phase III. Our results support the hypothesis that RBC adsorption with the RBC and fibroblast-coating methods represents a cell surface marker for division age and senescence of human diploid cells, respectively, at the individual cell level.     

Glucose-6-phosphate dehydrogenase activity in individual rat hepatocytes of different ploidy classes. I. Developments during postnatal growth

The glucose-6-phosphate dehydrogenase (G6PDH) activity of isolated male rat hepatocytes has been investigated in relationship to the ploidy classes of the cells during the first 20 weeks of postnatal growth. The G6PDH activity in the individual cells was measured with an improved quantitative cytochemical method. The data obtained showed that throughout the whole period of postnatal growth there existed a proportional relationship between the genome copies per cell and the amount of G6PDH activity per cell for binuclear diploid (BD), mononuclear tetraploid (MT) and binuclear tetraploid (BT) cells but not for mononuclear diploid (MD) cells. In the MD cells, which are the stem cells of the liver parenchyma, the activity measured was 1.5 times higher than expected. Furthermore, during postnatal growth, the G6PDH activity per hepatocyte was low at the age of 2 weeks, increased somewhat after weaning (5 weeks) and then more dramatically after 8 weeks to reach a maximum between 12 and 16 weeks. This development occurred in MT and BT cells at an earlier age than in MD and BD cells, in which the increase in enzyme activity followed some 3 weeks later. Castration of the rats before puberty did not influence the development of the amount of G6PDH activity per cell of any of the ploidy classes.     

Insulin-like growth factor II binding and action in human fetal fibroblasts

To investigate the role of insulin-like growth factor II (IGF-II) in human prenatal growth, IGF-II binding and biological action were studied in four lines of fetal and three lines of postnatal human fibroblasts. Specific binding of IGF-II was similar in both groups: 15.7% and 14.9% for fetal and postnatal fibroblasts, respectively. This was 5-10 times the amount of IGF-I binding found in these cells. IGF-I and IGF-II caused dose-dependent increases in [14C]aminoisobutyric acid (AIB) uptake. IGF-II was sevenfold less potent than IGF-I in stimulating this metabolic response in both fetal and postnatal fibroblasts. The maximal effect of IGF-II in stimulating [14C]AIB uptake approach that of IGF-I. Similar results were obtained when IGF-I and IGF-II stimulation of [3H]thymidine incorporation was compared in fetal and postnatal fibroblasts. Incubation in the presence of alpha IR-3, a monoclonal antibody to the type I IGF receptor, inhibited the ability of both IGF-I and IGF-II to stimulate [14C]AIB uptake and [3H]thymidine incorporation in fetal and postnatal cells. A monoclonal antibody to the insulin receptor did not affect IGF action. These data indicate that IGF-II is a potent metabolic and mitogenic stimulus for human fetal fibroblasts. However, despite the presence of abundant type II IGF receptors on both fetal and postnatal human fibroblasts, IGF-II stimulation of amino acid transport and DNA synthesis appears to be mediated through the type I rather than through its own type II IGF receptor.